Many integrated circuits rely on precision measurements of various signals to ensure proper functionality. For example, a temperature sensor may rely on accurate voltage measurements in order to correctly identify a given temperature. In order to determine the actual value of a signal, the measured value of a signal is compared to a reference signal having a known value. The difference between the known value of the reference signal and the measured value is used to determine the actual value of the signal. The comparison may be performed, for example, using an analog-to-digital converter (ADC).
In certain systems, a ground reference voltage is brought on to a chip through an input/output (I/O) pad. The ground reference voltage is used with an on-chip bandgap reference voltage generator to generate a bandgap reference voltage used as a reference signal input to an ADC. The ADC can use the reference signal to make any number of signal measurements. However, current flow in the ground path through the bandgap reference voltage generator can create errors in absolute accuracy measurements in relation to the ground reference voltage. Metal routes used to carry signals in the chip have a nominal parasitic resistance. When current flows through the metal routes, a voltage drop occurs across the parasitic resistance. This voltage drop may change the value of the bandgap reference voltage and the value of an on-chip ground voltage, causing any measurement made by the ADC to be inaccurate compared to actual values.